A CMOS (complementary metal oxide semiconductor) image sensor is a device that can detect outputs of pixels in a switching manner. In a CMOS image sensor, MOS transistors formed in each unit pixel are manufactured using CMOS technology. A control circuit and a signal processing circuit are used as peripheral circuits, and the outputs of the pixels are sequentially detected using the MOS transistors.
As the number of pixels of a CMOS image sensor increases, the size of the pixels decrease.
Reduction in the size of the pixel limits the size of a microlens that can be disposed on the pixel, and thus shortens the focal length of the microlens. Therefore, the size of a metal line layer forming a logic circuit around the pixel is limited.
As the number of pixels of an image sensor increases, a micro-wiring process becomes necessary to increase the size of a pixel region.